Welcome to the official world of words, tweet. And to you, walk-off. Also to you, bromance.

These are among 150 new words defined in the latest edition of Merriam-Webster’s Collegiate Dictionary. The authoritative lexicon has been around for 150 years and it moves with the times. With each succeeding edition, it certifies that new words, phrases and slang expressions have become a part of the language.

Thus, tweet: not just the sound of a canary, but a short electronic communication sent simultaneously to everyone else living in your particular bird’s nest. Or, walk-off: What commentators call a home run or other hit that causes a game-winning run to cross the plate in the bottom of the ninth inning (baseball should have its own dictionary).

Bromance? It seems to be "a close nonsexual friendship between men."

As new words enter the vocabulary, others become obsolete. One we would like to see enter its twilight years is the use of "event" as par...